Halo 4 since you can be playing the multiplayer much longer then AC3. Also AC is known to have price drops in the upcoming months, and unless you played all AC up to AC3, you may be confused at some bits.
Regardless of all, the single player is the best for Halo 4 and they might be starting another trilogy

Life would be a lot better if don't have to make choices. I know it would make my life easier.

Think of the one that would be the longest single player campaign. Then think of which one you will have the most fun with. I choose games based on single player worthiness. While both are good, Halo 4 may be starting a new trilogy while AC3 continues. AC3 might drop in price and you could get away with a cheaper buy if you can wait a bit.

Life would be a lot better if don't have to make choices. I know it would make my life easier.

Think of the one that would be the longest single player campaign. Then think of which one you will have the most fun with. I choose games based on single player worthiness. While both are good, Halo 4 may be starting a new trilogy while AC3 continues. AC3 might drop in price and you could get away with a cheaper buy if you can wait a bit.

Well I made my choice and got halo 4, it's fucking awesome. The only bad thing is is that you have to install multiplayer on the second disk. Other than that I think it's better than assassins creed, a lot better.

Well I made my choice and got halo 4, it's fucking awesome. The only bad thing is is that you have to install multiplayer on the second disk. Other than that I think it's better than assassins creed, a lot better.

Actually Assassin Creed 3 its multi-disk. 1 for single player and second for multiplayer, either or good choice

I would go with AC3 it looks so much better than AC revelations and game play is pretty smooth. Not to mention the fact its during the American Revolution . If you have a PS3 get it for the PS3 looks way better on it IMO. But yea it seems like a hard choice seeing as probably most of your friends on the 360 will get Halo 4 and you'll want to play with them.

Im leaning towards halo. I currently own AC1 and AC2 and played about an hour on the first and found it very repetitive and ragequit... Now that 3 is supossed to be amazing, im stuck without a story line(guess ill be waiting for the movie...)

Doesn't matter, Unreal takes it all. Halo CE had some the best thing in multiplayer. Halo 3 perfected multiplayer on console. Only reason to get Halo 4 is the story, still don't know if they made the multiplayer better than Halo 3. Since AC2 i enjoyed the IP and hope to have more of this title.
Still you can expect one thing, someone somewhere is your father and slept with your mother while discussing your sexuallity and the race you represent....Xbox Live